"Half fill a bright frying pan with boiling water; add a salt spoonful of salt and two teaspoonfuls of vinegar; break each egg separately into a cup, pour them carefully into the water while boiling; with a small slice throw the white over the yolk; drain for half a minute, then serve either on hot buttered toast, or on spinach or sorrel. Two and a half or three minutes will be sufficient time to give them."
From The Young Housewife's Daily Assistant 1864
Notes: My salt spoon holds just less than 1/2 teaspoon. I used white vinegar, as I found it mentioned in other cook books of the time. I am assuming that a "slice" is a slotted spoon and was able to find a reference; "passing the slice or a spoon". I used a lined copper frypan as cast iron is not good to boil water in.
Over all, it really wasn't hard to do. I just made 2 eggs for myself and they turned out beautifully. The key is to not have the water boiling when you add the eggs and to gently add them to the water. Otherwise, if you add the egg too fast, it will slide to the other side of the pan and stream the white behind it. As I had no spinach or sorrel, I ate my poached eggs on modern toast with salt and pepper.
Mrs. Beeton also gives her own instruction for making poached eggs here along with an explanation of the importance of fresh eggs and an illustrations of a tin egg-poacher .